Method of obtaining mica



Feb. 21, 1950 w. TTso 2,498,111

METHOD OF OBTAINING MICA Filed Dec. 6, 1945 Patented Feb. 21, 1 950UNITED STATES PATENT OFFICE METHOD OF OBTAINING MICA William M. Mattson,Concord, N. 11., assignor to Concord Mica Corporation, Concord, N. H., acorporation of New Hampshire Application December 6, 1945, Serial No.633,074

2 Claims. 1

The method pertains to an improvement in methods heretofore employed forobtaining mica by wet grinding of the scrap from which the mica isobtained and especially a method employing a centrifuge for dehydration.

Among the objects of the invention are:

To increase the amount of mica recovered from any treated batch ofmaterial, and with as little waste as possible.

To conserve in the use of water; not by using less water but by savingthe water that has been used.

The method entails various steps which can best be understood in thelight of the apparatus that is employed for practicing them, and whichapparatus. for the most part diagrammatically illustrated, is shown inthe drawings, inwhich Fig. 1 is a plan of the apparatus used inpracticing the method.

Referring to the drawings, l represents one or more so-called grindingor delaminating mills, of a type like those previously employed, andwith interior mechanism (not shown) acting upon the contained mass inthe mill in the presence of water to delaminate or split the micaparticles.

The action of the grinding mill is not to destroy the laminal structureof the mica but is a delaminating action, this by an impact or kneadingaction and friction of one piece on another, thereby reducing the mice,to minute plates or flakes of assorted diameters, some coarse and somefine, with a maximum thickness for each plate or flake of from one totwo microns.

The operation effected by the grinding mills is a more or lessprotracted action on the completion of which there is obtained a mass ofmica which is flushed from the grinding mill by a further addition ofwater in which the mica lies in such suspension that it may be piped forfur ther processing. There is also some considerable foreign matterwhich is removed by any suitable practice previously employed.

From the grinding mill, or mills, the water in which lie suspended theparticles or flakes of mica, is conveyed through a pipe, or pipes, 2 toan agitating tank, or tanks, 3. Two or more of these tanks arepreferably employed connected with one another in order that an amplesupply of material to be dewatered may be maintained at all times, andespecially during the processing of new material introduced into thegrind-- ing mills, the dewatering of ground material going onduring suchperiod. Each of the tanks has associated with it a power controlledagitating mechanism (as shown) which keeps the conwithdrawn fordewatering.

The dewatering is effected by a centrifugal machine into which thecontent of one of the agitating tanks is directed through a pipe 5. Thisaction is effected by means of a pump 6 and the pipe is also fitted withany suitable cutoff valve 1.

The centrifuge is one of common type having a rotated basket 8 into theinterior of which the pipe 5 extends for discharging the matter passingthrough it. The action of the centrifuge is to throw by centrifugalforce against its sides the mica particles introduced into it, whichparticles build up or accumulate along and within the side of thebasketin a dewatered mass, and the waste water is thrown out through theopen top of the basket.

While the centrifuge is most economical and efficient in recovering thecoarser and larger mica plates or flakes which carry with them aconsiderable quantity of the finer and smaller mica flakes, yet I havediscovered that there remains a large percentage of the finer andsmaller mica flakes not taken up by the heavier particles, and which areso small and lacking in weight as to be incapable of being thrownlaterally in their initial passage through the machine as the heavierparticles are thrown into the dewatered mass but will remain suspendedin the waste or extracted water and accordingly will pass out throughthe top of the basket in this water. In consequence, according to thepresent method, the waste water expelled from the centrifuge to the topof its basket is collected by entry into a chamber 9 built around thebasket and thence directed through pipes Ill into settling tanks ll.Passage through these pipes for any and all the settling tanksiscontrolled by valves I2. I prefer to employ a number of these settlingtanks with total capacity suflicient to receive and hold substantiallyall water introduced into the grinding mills that has been previouslyused for effecting the grinding operation and for flushing these mills.

The mice, that has accumulated within the basket of the centrifuge isremoved after closing the valve in the pipe 5 leading from the agitatingtank from which the feed is madeto the centrifuge. Thereupon the micaaccumulated within the basket of the machine is removed in the usualmanner by shovels (not shown) which form a part of the machine.

The matter introduced into the settling tanks is allowed to settle,leaving an accumulated mass of mica particles, or sludge, at the bottomand an accumulation of water above, though this accumulated water mayhave some fine mica particles within it.

The settling or sludge at the bottom is pumped back into one of theagitating tanks, preferably the one from which the feed is directed tothe centrifugal machine. The accumulated mica sludge is thus directedinto the agitating tank in order that the fine mica particles in thesludge may be taken up by the heavier mica particles 7 in the agitatingtank and be carried to the centrifugal machine and be thrown off bycentrifugal force. In this connection full advantage is taken of theexcellent adhesive qualities of the fine mica flakes, which aresuspended in the waste water, or sludge, to adhere to the heavierparticles in the agitating tank. Mica flakes have an affinity orattraction for each other and will stick or cleave together so that theheavier mica particles in the agitating tank will take up and carry thefiner particles, thus making possible the continuous process ofeventually recovering all the fine mica plate or flakes obtained by theinitial grinding, and formerly wasted in their passage through thecentrifugal dewatering machine.

The accumulation of water in the settling tanks left after the settlingof the mica flakes is pumped back into the grinding mills to be usedboth for the watering of fresh stock and for flushing these mills asoccasion requires. Water from the settling tanks may also be pumped backinto the agitating tank from which the feed is made to the centrifuge ifand when this tank requires an extra supply of water.

Any suitable means may be provided for disposing of the contents of thesettling tanks as previously referred to. In practice a pipe section 13leads from that bottom portion of each of the settling tanks whichcontains the sludge. The passage through this pipe section is controlledby a valve 14. Another pipe section l5 leads from that portion of eachof the settling tanks which contains the water content lying above thesettling. The passage through this pipe section is controlled by a valvel6. Both the pipe sections I3 and I5 connect with a common pipe llleading to the inlet of a pump l8. Extending from the outlet end of thispump is a pipe section l9 connecting to a pipe section having branches20 and 2| extending in different directions, one the pipe section 20extending to the agitating tank 3 with a valve 22 for controlling thedischarge into this tank, and the other branch 2| extending to connectwith the grinding mills through pipe s:ctions 23. Passage through thebranch section 2| is controlled by a valve 24 and the passage to each ofthe grinding mills through the pipe section 23 is controlled by a valve25. Obviously by the opening and closure of certain of those valves thesludge in any or all of the receiving tanks may be pumped into theagitating tank, and by the opening and closure of certain other of saidvalves the water in any or all of the settling tanks may be pumped intoany or all of the grinding mills, or into the agitating tank, asoccasion may require.

After dewatering by the centrifuge all recovered mica is dried andscreened in the usual manher.

I claim:

1. In the process of obtaining mica from micaceous stock by wet grindingand in which a centrifuge is employed to which water with micaceousmatter is delivered for purpose of dehydration and from which centrifugewater containing small particles of micaceous matter unhydrated by thecentrifuge is discharged, the steps of recovering the micaceous matterin the water so discharged which comprises collecting the waterdischarged from the centrifuge containing the small particles ofmicaceous matter as aforesaid and allowing such matter to settle in thewater so collected to form a sludge, subjecting this sludge bysuspension in water to the presence of larger ground particles ofmicaceous matter capable of dehydration in a centrifuge and agitatingwhereby the larger particles will take up the smaller particles of thesludge and afterwards delivering the lar er particles of micaceousmatter bearing the smaller particles obtained from the sludge to thecentrifuge for purpose of dehydration.

2. In the obtaining of mica from micaceous stock employing among otherelements a grinding mill for reducing the stock in the presence of waterand a centrifuge to which water with micaceous matter is delivered forpurpose of dehydration and from which centrifuge water containing smallparticles of unhydrated micaceous matter is discharged, the steps ofrecovering the water and small particles of micaceous matter in itdischarged from the centrifuge which comprises collecting the waterdischarged from the centrifuge containing the small particles ofmicaceous matter as aforesaid and allowing such matter to settle in thewater so collected to form a sludge with supernated water above thesludge, returning the supernated water to the grinding mill andsubjecting the sludge by suspension in water to the presence of largerground particles of micaceous matter capable of dehydration in acentrifuge and agitating whereby the larger particles will take up thesmaller particles of the sludge and afterwards delivering the largerparticles of micaceous matter bearing the smaller particles obtainedfrom the sludge to the cen trifuge for purpose of dehydration.

WILLLIAM M. MA'I'ISON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Atwood June 11, 1940 OTHER REFERENCESNumber

